1982/09/01 by William M. Hamner, Ronald W. Gilmer, Peggy P. Hamner · 4 citations
Earth and Planetary Sciences · Environmental Science · #Marine Invertebrate Physiology and Ecology #Aquatic Ecosystems and Phytoplankton Dynamics #Aquatic Ecosystems and Biodiversity
paper · pdf · doi:10.4319/lo.1982.27.5.0896
openalex publication_date 1982/09/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/26
Eil Malk Jellyfish Lake in Palau is a 5‐ha, 30‐m deep, meromictic saline lake, stratified, with anoxic hypolimnion, damped, delayed tides, and no heat accumulation. The top 15 m are oxygenated, nutrient‐poor but turbid, with high primary productivity and large planktonic populations of only five metazoans: the medusae Mastigias and Aurelia, the copepods Oithona and Acrocalanus, and silverside fish, Pranesus. At the chemocline a floating bacterial plate dominated by photosynthetic purple bacteria ( Chromatium ) degrades and solubilizes almost all particulate material and absorbs all sunlight. Below the plate the anoxic, clear water contains extremely high levels of NH 4 + , H 2 S, and PO 4 3− . Sediments are primarily undisturbed fish fecal pellets full of copepod exoskeletons. The lake is stable, aseasonal, and shows no obvious cycles of the populations. An unusual horizontal and vertical swimming behavior of Mastigias appears related to light and to the nutrient requirements of its symbiotic zooxanthellae. Other zooplankton show normal vertical diurnal migration patterns. Facultafive schooling by Pranesus reflects the absence of predators in the lake.